As is known, tapping molten metal from the electrolysis potlines or furnaces of primary aluminium, or from the smelting furnaces of special metal alloys, involves highly critical operations especially in respect of safety and operating economy. In fact, particularly for tapping aluminium from electrolysis furnaces, steel crucibles are used which are lined internally with refractory and provided with a sealing lid, and commonly referred to as ladles. Disposed on the ladle lid is a shaped tube which is dipped into the molten metal contained in the electrolysis cells, thereby on applying a vacuum to the ladle by means of compressed air evacuator, or some other arrangement, connected to an opening in the lid, the molten aluminium is caused to flow up into the ladle through said shaped tube. It follows that, when tapping is required, the ladle must be moved close to the furnace, and after filling, be moved away and transported to the collecting furnaces grouped in the foundry area. Since the smelting furnaces are usually laid, in the potline room, in parallel lines, either as rows or arrays of furnaces, leaving between rows or arrays access passages which are allowed to be fairly narrow for space saving reasons, the ladle handling operations become complicated, unpractical, and even hazardous for the operators.
To move a ladle close to the casting furnace and take it to the foundry, it is current practice to use bridge cranes running parallel to the cell rows, or alternatively, self-propelled fork, crane, or the like trucks.
In actual practice, both the use of bridge cranes and self-propelled crane or fork trucks involves serious problems and limitations to their operation, additionally to the fact that at least two operators are required in such cases.
In fact, a bridge crane only allows for transportation of the ladles along a straight path over the potline, and consequently, all the movements of the ladles to and from the molten metal collecting furnace at the foundry must be effected using fork or crane vehicles. Transportation with fork or crane vehicles is a difficult and hazardous operation on account of the movements which take place in the molten mass within the ladle during transportation and of the location of the ladle which, being usually placed in front of the vehicle operator, is apt to restrict his visibility and hinder the moving operations.
Lastly, both the bridge cranes and the fork or crane trucks, additionally to being unwieldy and generally inconvenient to use in the passages between rows of smelting furnaces, involves the availability of complex and expensive permanent installations.